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We have used a sample of photon+3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb−1 to determine the fraction of events with double parton scattering (f{sub DP}) in a single ppbar collision at √s = 1.96 TeV. The DP fraction and effective cross section (sigma{sub eff}), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p{sub T}) jet transverse momentum pT{sub jet2} within the range 15
Samples of inclusive [gamma] + 2 jet and [gamma] + 3 jet events collected by the D0 experiment with an integrated luminosity of about 1 fb−1 in p{bar p} collisions at √s = 1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p{sub T}) of the [gamma] + leading jet system (jets are ordered in p{sub T}) and p{sub T} of the other jet for [gamma] + 2 jet, or p{sub T} sum of the two other jets for [gamma] + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the pythia and sherpa Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well described by predictions provided by the pythia MPI models with p{sub T}-ordered showers and by sherpa with the default MPI model. The [gamma] + 2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet p{sub T}.
The thesis is devoted to the study of processes with multiple parton interactions (MPI) in a ppbar collision collected by D0 detector at the Fermilab Tevatron collider at sqrt(s) = 1.96 TeV. The study includes measurements of MPI event fraction and effective cross section, a process-independent parameter related to the effective interaction region inside the nucleon. The measurements are done using events with a photon and three hadronic jets in the final state. The measured effective cross section is used to estimate background from MPI for WH production at the Tevatron energy.
This book mainly focuses on the study of photon + 3 jets final state in Proton-Proton Collisions at √s = 7TeV, searching for patterns of two (or more) distinct hard scatterings in the same collision, i.e the so-called Double Parton Scattering (DPS). A new method by using Monte Carlo generators was performed and provides higher order corrections to the description of the Single Parton Scattering (SPS) background. Further it is investigated whether additional contributions from DPS can improve the agreement between the measured data and the Monte Carlo predictions. The current theoretical uncertainties related to the SPS background are found to be larger than expectation. At the same time a rich set of DPS-sensitive measurements is reported for possible further interpretation.
We consider sample of inclusive [gamma] + 3 jet events collected by the D0 experiment. The double parton fraction (f{sub DP}) and effective cross section [sigma]{sub eff}, a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p{sub T}) jet transverse momentum p{sub T}{sup jet2} within the 15 ≤ p{sub T}{sup jet2} ≤ 30 GeV range. Also we measured cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p{sub T}) of the [gamma] + leading jet system and p{sub T} of the other jet for [gamma] + 2 jet, or p{sub T} sum of the two other jets for [gamma] + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators.
Kinematic properties of four-jet events in p[bar p] collisions at [radical]s = 1.8 TeV are compared with the predictions of leading order quantum chromodynamics. We place an upper limit on the double parton scattering cross of [sigma][sub DP] 120 nb (95% C.L.) for partons with transverse momenta greater than 18 GeV/c. Defining the effective cross section [sigma][sub eff] through the equation of [sigma][sub eff] = [sigma][sub DP] = [sigma][sub dijet]/([sup 2]/[sigma][sub eff]), where [sigma][sub dijet] is the cross section for two-jets events, the limit [sigma][sub eff] 3.9 mb (95% C.L.) is also placed. Implications for physics at the SSC ([radical]s = 40 TeV) are discussed.
This thesis addresses in a very new and elegant way several measurements and the extraction of so-called double parton scattering. The new and elegant way lies in the combination of measurements and a very smart extraction of double parton scattering results, which is easy to apply and overcomes many of the technical difficulties of older methods. Many new phenomena in particle physics can be observed when particles are collided at the highest energies; one of the highlights in recent years was the discovery of the Higgs boson at the Large Hadron Collider at CERN. Understanding the production mechanism of the Higgs boson at the LHC requires detailed knowledge of the physics of proton-proton collisions. When the density of partons in the protons becomes large, there is a non-negligible probability that more than one parton participates in the interaction and the so-called double parton scattering becomes important. In some cases very particular final state signatures can be observed, which can be regarded as an indication of such double partonic scattering and where the different interactions can be separated. Such multiple partonic interactions play an important role when precise predictions from known processes are required.